Nature Geoscience 2, 234 - 236 (2009)
Since the end of the Apollo era, the Moon has received relatively little attention from planetary scientists. Fresh interest from a new range of nations could lead to insights into our satellite's evolution and resources.
Since the pioneering Apollo missions ended the first phase of intense lunar exploration some three decades ago, lunar samples and remote sensing data have continued to yield a first-order understanding of the Earth's only major natural satellite1, 2. Two robotic missions to the Moon in the 1990s, Clementine3 and Lunar Prospector4, provided us with global maps of the chemical and mineralogical composition of the surface, topography, gravity and other properties that have greatly expanded our understanding5. In particular, the missions revealed that the lunar poles are special environments: the interplay of the unique illumination conditions and cratered topography at the poles means that some parts receive constant sunlight and others remain permanently dark. As a result, the poles experience marked contrasts in temperature, which could have affected the accumulation and retention of volatile elements such as hydrogen. Clementine and Lunar Prospector also reminded us that there is much about this rocky body that we do not know. For example, neither the abundance of the volatiles at the surface, nor the causes of the Moon's compositional diversity — and hence its history — are fully understood.
At present, the Moon is experiencing a new round of exploration by an international flotilla of mapping spacecraft. The SMART-1 mission of the European Space Agency, Chang'E of China, Kaguya of Japan and Chandrayaan-1 of India have all recently mapped the Moon and some continue to do so (Box 1; Fig. 1). Equipped with sophisticated second-generation sensors, these spacecraft are yielding insights into the detailed topography, composition and environment of the Moon6, 7, 8, 9.